The invention is directed to a method for manufacturing a texture drum, whereby a surface structure is produced in the surface region of the texture drum with an electron beam. The invention is also directed to an apparatus for the implementation of the method.
In the past, various methods have been employed for manufacturing such texture rollers or skin-pass rollers that, in particular, are employed for producing a surface structure on sheet steel. On the one hand, particle charging with steel pellets corresponding to a scrap metal shot occurred; second, depressions were implemented in the surface region of the texture drum with the assistance of electro-erosion or with the assistance of lasers. The electro-erosion and the particle charging with steel pellets, however, lead to depressions limited with sharp edges whose edge regions tend to break off and, thus, tend to develop dust. Over and above this, an oxidation of the drum metal and, thus, a formation of ash arise in electro-erosion and in laser charging. The number of depressions to be produced on the drum surface when carrying out a processing with lasers is limited by the inertia of the mirrors employed.
German Published Application 28 40 702 discloses a method and an apparatus for improving the quality of fine sheet steel. It is recited in this publication that a surface structure on the drum surface occurs with the assistance of an intermittent energy beam along a helical path. In particular, it is recited that a laser beam can be employed as an energy beam. However, it is also already pointed out that an electron beam can be fundamentally employed. Specific teachings directed to the execution of a method upon employment of an electron beam or for building an apparatus that employs this method are not, however, provided.
EP-A-0 119 182 discloses that a drum surface is charged with the assistance of a laser beam or an electron beam. A helical path in the region of the drum is produced with the assistance of this radiation. In particular, it has been envisioned here to blow a gas, for example oxygen, into the region of the beam charging. An oxidation of the drum metal occurs in the region of the beam charging due to the presence of oxygen. The formation of a crater wall that surrounds a recess generated by the radiation is thereby largely avoided since the material evaporating from or hurled from the recess in a liquid state reacts very quickly with the oxygen.
French Patent 902 850 discloses that a surface structuring be implemented in the region of a texture drum with the assistance of laser emission and that the employment of mirrors be avoided since the texture drum to be charged is rotationally and translationally moved past a stationary laser.
The texture drums manufactured with the known method do not allow any satisfactory useful lives since an intensification of the pressing power during operation is required due to a relatively quickly decreasing roughness of the drum surface. This higher pressing power, however, leads to other sheet metal properties, particularly to changes of the hardness and in the bending properties. Since these changes occur during production, constant product properties cannot be guaranteed.